Generally, submerged portions of ships and marine structures are provided with antifouling coating for the purpose of preventing corrosion or the drop of cruising speed of the ships due to the attachment of marine organisms such as barnacles, teredos, and algae. Such antifouling coating is also applied to fishing nets used for cultivation to prevent fatal condition of fish and shellfish due to the attachment of the marine organisms on the nets.
An antifouling substance is typically contained in the antifouling coating. An antifouling effect is shown by elution of the substance in seawater. When a disintegrating type antifouling coating comprising a rosin composition is immersed in seawater for a long period of time, the eluting substance is gradually decreased and the proportion of non-eluting component is increased in the coating, and at the same time the surface of the coating becomes uneven, consequently, there is a tendency of large reduction in an effect of preventing adhesion of organisms such as marine organisms and the like. In the case of hydrolysis-type antifouling paint, the coating surface is gradually dissolved away to renew the surface (self polishing) constantly, so that the antifouling substance will be always kept exposed on the coating surface to allow longtime retention of its antifouling effect. This type of antifouling paint, however, tends to contain a large quantity of the antifouling substance to keep the above-mentioned property. Therefore, antifouling paint which can show the property even if it contains less or none of the antifouling substance is under investigation.
For example, JP-A-62-57464 and JP-A-62-84168 describe hydrolysis-type antifouling paints using a copolymer having metal-containing groups at the end of its side chains. JP-A-11-35877 and JP-A-2002-012630 describe self polishing type paint compositions containing a copolymer, as a vehicle, comprising a metal-containing polymerizable monomer and an antifouling agent.
JP-A-62-252480, JP-B-63-2995, JP-A-5-78617, and JP-A-5-287203 describe antifouling paint compositions using reactive curable (crosslinkable) silicone rubber containing silicone oil, silicone resin having hydroxyl group, or polysiloxane having silanol group. JP-A-62-156172 describes an antifouling paint composition containing a polymer having polydimethylsiloxane group as a side chain to form a coating having a property of low surface tension of the polymer.
Further, JP-A-2001-72869 describes a paint composition using a copolymer having polysiloxane structure and a metallic salt of specific organic acid group as side chains to form a coating which shows the antifouling effect even if an antifouling agent is not contained in it.
However, it is necessary for the antifouling paints using metal-containing copolymers described in JP-A-62-57464, JP-A-62-84168, JP-A-11-35877, and JP-A-2002-012630 mentioned above to contain a large quantity of the antifouling substances to obtain the antifouling effect sufficiently.
It is difficult for the antifouling paints using the property of low surface tension described in JP-A-62-252480, JP-B-63-2995, JP-A-5-78617, JP-A-5-287203, and JP-A-62-156172 to keep the low surface tension in seawater and to show the antifouling effect for a long period of time, and these paints have a problem of low adhesion to a substrate.
Though the copolymer used in JP-A-2001-72869 is obtained by reacting monovalent organic acid residues and bivalent metallic oxides on the side chains of copolymer having polysiloxane structures and carboxyl groups, it is not easy to add metal atoms to the carboxyl groups. As a result, it tends to be difficult for the paint using the copolymer to show the self polishing stability and the antifouling effect for a long period of time. And the paint has a problem of low adhesion to a substrate, and it also has a problem of deterioration of the antifouling effect when a pigment is added to a coating composition containing the copolymer.